This invention relates generally to signposts and, more particularly, to breakaway signposts for signs adjacent to roadways.
A roadway sign typically includes an anchor that is driven into the ground, an extended support connected to the anchor and extending above the ground, and a sign attached to the support. Due to their proximity to the roadway, road signs may be a hazard for errant vehicles.
The Federal Highways Administration (“FHWA”) has promulgated yielding criteria for signposts and structures located adjacent to designated traffic areas both to protect the occupants of vehicles and to reduce property damage from collisions with these structures. For small and intermediate roadside supports, the FHWA standards required a structure weak enough to bend upon impact and allow a vehicle to pass over the support structure with minimum deceleration. Thus, occupant interior impact could be avoided and vehicular damage could be minimized. After a collision, however, the entire roadway sign support needs to be replaced, including the anchor in many cases.
To avoid the cost of replacing the anchors after a collision, signposts have been designed in which the sign support shears from the anchor upon impact so that the anchor may subsequently be reused with a replacement support after a collision. Couplers machined or cast with predetermined break points, such as shear bolts, have been employed with some success to separate the sign support and the anchor so that the anchor is undamaged when a vehicle collides with a signpost. However, the couplers are vulnerable to shearing from wind loads on a sign.